1. Field of the Invention
The present invention generally relates to tape cassettes and, more particularly, is directed to a tape cassette having a reel locking member for preventing the rotation of a tape reel or locking the tape reel when the cassette is not in use, and having a locking member for locking when the cassette is not in use a guard panel which opens and closes a tape exposing portion provided at a front face of the tape cassette.
2. Description of the Prior Art
The structure of an example of conventional tape cassettes for a video tape recorder (VTR) will be explained with reference to FIGS. 1 to 5B.
Referring to FIGS. 1 to 5B, a cassette casing 2 of a tape cassette 1 is formed by fixedly integrating an upper half 3 and a lower half 4. A pair of tape reels for winding a tape (magnetic tape) T, that is, a supply reel 5 and a take-up reel 6 are rotatably accommodated in the cassette casing 2. The tape T extended from the supply reel 5 is exposed at a tape exposing portion 8 which is provided at a front face of the cassette casing 2 through tape guides 7a and 7b, and then wound by the take-up reel 6 through tape guides 9a and 9b.
A guard panel 11 is provided at the front face of the cassette casing 2 in order to protect the tape T exposed at the front face. The guard panel 11 has side panels 11a provided at both sides thereof which are pivotally supported by the cassette casing 2 so that the guard panel 11 is swingable upwardly and downwardly. When the cassette is not in use or is not mounted in a VTR, the guard panel 11 is located at a position shown in FIG. 1 to close the tape exposing portion 8 so as to protect the tape T. When the tape cassette 1 is mounted in the VTR, the guard panel 11 is rotated upward by a mechanism of the VTR to expose the tape exposing portion 8.
A reel locking mechanism 12 is provided within the cassette casing 2 at its rear center portion so as to prevent the rotation of or lock both the reels 5 and 6 to thereby prevent the tape from unwinding when the tape cassette 1 is not in use. The reel locking mechanism 12 has a pair of reel locking members 13 and 14 disposed in association with the supply reel 5 and the take-up reel 6, respectively, and an operating member 15 for pressing the reel locking members 13 and 14. The reel locking members 13 and 14 are pivotally supported by pivots 16 and 17 which are implanted upwardly on the lower half 4 of the cassette casing 2. The reel locking members 13 and 14 have engaging ratchets 13a and 14a for engaging respectively with teeth 5a and 6a formed on the outer peripheries of the reels 5 and 6 and operating rods 13b and 14b which abut against the operating member 15. The engaging ratchets 13aand 14a and the operating rods 13b and 14b are integrally formed.
A pin 18 is projected upwardly from the lower half 4 at an intermediate position between the reel locking members 13 and 14, and a torsion coil spring 19 made from stainless material is wound around the pin 18. Opposite arm portions of the torsion coil spring 19 engage with engaging projections 20 and 21 formed on the reel locking members 13 and 14, respectively. Thus, the reel locking members 13 and 14 are rotatably biased by the torsion coil spring 19 to swing in such directions that the engaging ratchets 13a and 14a engage respectively with the tooth 5a and 6a of the reels 5 and 6 as shown in FIG. 4A. Accordingly, each of the reels 5 and 6 is prevented from rotating to thereby prevent the tape from unwinding.
When the tape cassette 1 is mounted or inserted in the VTR, a releasing member (not shown) provided in the VTR comes into the tape cassette 1 through a through hole 22 of the lower half 4 to push the operating member 15, so that the operating member 15 presses the operating rods 13b and 14b of the reel locking members 13 and 14. Thus, the reel locking members 13 and 14 swing against the spring-biasing force of the torsion coil spring 19 in such directions that the engaging ratchets 13a and 14a disengaged from the teeth 5a and 6a of the reels 5 and 6 so that each of the reels 5 and 6 is unlocked and becomes rotatable as shown in FIG. 4B.
A guard panel locking mechanism 23 is provided within the cassette casing 2 at its front corner portion so as to hold the guard panel 11 in a closed state when the tape cassette 1 is not in use as shown in FIG. 5A and 5B. The guard panel locking mechanism 23 mainly comprises by a guard panel locking member 25 which is pivotally supported by a pivot 24 projected upwardly from the lower half 4 of the cassette casing 2. The guard panel locking member 25 has an engaging ratchet 25a and an operating projection 25b which are united together. The engaging ratchet 25a and the operating projection 25b are arranged so as to protrude out of the cassette casing 2 through through-holes 26a and 26b formed through a side panel 4a of the lower half 4. An engaging recess 27 is formed on an inner side of a side panel 11a of the guard panel 11 in correspondence with the engaging ratchet 25a of the guard panel locking member 25.
A torsion coil spring 28 is wound around the pivot 24 by which the guard panel locking member 25 is pivotally supported. One arm portion of the torsion coil spring 28 engages with an engaging projection 29 of the guard panel locking member 25 and the other arm portion of thereof engages with an engaging projection 30 provided on the inner side of the side panel of the lower half 4. Thus, the guard panel locking member 25 is always biased by the torsion coil spring 28 to swing in such a direction that the engaging ratchet 25a and the operating projection 25b protrude out of the side panel of the lower half respectively through the through-holes 26a and 26b.
When the guard panel 11 is closed, the engaging recess 27 of the side panel 11a thereof engages with the engaging ratchet 25a of the guard panel locking member 25, so that the guard panel 11 is locked such that it cannot swing open, as shown in FIG. 5A. When the tape cassette 1 is loaded onto the VTR, a releasing member (not shown) of the VTR comes into the tape cassette 1 to push the operating projection 25b of the guard panel locking member 25. Thus, the guard panel locking member 25 swings inward or counterclockwise in FIG. 5A against the spring-biasing force of the torsion coil spring 28 so that the engaging rachet 25a goes out of the engaging recess 27. Hence, the guard panel 11 is released from the locked state and becomes rotatable, as shown in FIG. 5B.
Recently, in order to reduce cost and improve productivity in making the above-described tape cassette, spring or elastic portions such as plastic springs have been unitarily formed as biasing means with the reel locking members 13, 14 and the guard panel locking member 25 to thereby eliminate the torsion coil springs 19 and 28. However, this has resulted in the position that the spring portions are deformed due to creep load applied thereto in the VTR. That is, when the tape cassette is inserted in the VTR, the reel locking members 13, 14 and the guard panel locking member 25 are placed in such states that the reels 5, 6 and the guard panel 11 are released from the locked states, respectively, so that a creep load is kept applied to each of the spring portions. Since, in general, temperature within the VTR is high, the plastic is likely deformed. Thus, if the spring portions are kept biased by the creep load for a long period of time in the VTR, the spring portions are deformed to such a degree that they do not act as springs and can not recover their original configurations. As a result, each of the reels 5, 6 and the guard panel 11 can not be locked reliably after the tape cassette is ejected from the VTR.